This invention relates, in general, to manufacturing processes for electronic components, and more specifically, to an improvement in retaining insulated electrically conductive wires in what are commonly termed "printed circuit boards" preparatory to soldering. Printed circuit boards commonly comprise a board of insulative material having a thickness of about 1/16th of an inch. On at least one surface of the board is printed or otherwise impressed a plurality of terminal points consisting of a conductive material having a hole therethrough. The terminal points in turn are selectively interconnected by conductors commonly overlaid with an insulative substance. The holes may differ in diameter to accommodate wire of different gauges.
It is common practice to attach a lead to a printed circuit board terminal by removing the insulation from the tip of the lead, inserting the wire member in the desired hole, and crimping or otherwise deforming it so that it cannot easily be withdrawn from the hole. The retention is intended to be a temporary expedient, as the permanent electrical connection and mechanical attachment of the wire to the terminal is made by a soldering process, such as by dipping or wave-soldering.
A typical printed circuit board may have a great many terminals to which wires must be attached. Inserting the wires by hand and manually forming the protruding ends for retention by tool means such as pliers is a timely-consuming, labor-intensive process, and consequently high in cost.
Prior art means for providing for wire retention by printed circuit board terminals include the process of die-cutting of the tip of the wire and upsetting or partially cutting the wire to form a barbed hook which when inserted into terminal hole, inhibits withdrawal. The malformation due to the cutting of the wire by this process can result in the breaking of the wire. It is also known in the art to form the wire tip in serpentine configuration to inhibit lead withdrawal.
Another prior art means comprises the attachment of a preformed barbed connector to the wire tip as by crimping; the barbed connector, when inserted into the terminal hole, similarly inhibits withdrawal. The use of such a connector appreciably adds to the cost of manufacture because of the additional process steps of attaching the connector to the wire, and the cost of the connector itself.
Worth et al in U.S. Pat. No. 2,932,859 discloses means for making electrical connections between circuit components and circuits of the printed type. Shown are leads affixed to the rearward side of the printed panel by passing their wiring leads through holes in the panel and crimping them against the printed pattern terminal connections. Following the crimping operation such panels are dipped into a soldering bath to solder the crimped leads in place.